Network-layer soft vertical handoff schemes without packet reordering

With the integration of heterogeneous wireless technologies and the popularization of all-IP networks,network-layer soft handoff approaches have gradually evolved to improve the performance of vertical handoffs(VHOs).Unfortunately,the existing soft handoff approaches lead to plenty of out-of-order packets during downward VHOs.In this paper,the authors present a new network-layer soft vertical handoff scheme,called SHORDER.In the scheme,the mobile node(MN)starts or stops buffering packets from its new network based on a few interactive messages with its home agent(HA).With the buffering technique,the scheme can prevent mobile terminals from receiving reordered packets caused by downward VHOs,and is compatible with various transport-layer protocols and their variants due to its independence.Then,the authors theoretically analyze the influence of the proposed scheme on the handoff latency,the goodput and the congestion window of the TCP in comparison with a typical existing network-layer soft VHO method.Additionally,the authors also derive the applicable condition of the SHORDER scheme.Experiments show that the deployment of the proposed scheme is easy and the scheme has better performance under its applicable condition,further,experimental and analytical results are consistent with each other.Finally,based on the applicable condition of the SHORDER scheme,the scheme further is improved.

Performance Analysis of Trunk Network for Inter-MSC Soft Handoffs in CDMA Cellular Communication Systems

Code division multiple access (CDMA)-based radio-on-fiber road-vehicle communication systems were proposed to support real-time streaming services in intelligent transportation systems (ITSs). Soft handoff should be provided for real-time streaming services because these services are required to guarantee real-time property and quality of service (QoS). However, soft handoff of real-time streaming services causes the shortage of resource in view of the system. In this paper, the double-adjustment soft-handoff (DASH) scheme is proposed to support seamless service regardless of the shortage of resource and maximize the resource efficiency when real-time streaming services are served in CDMA-based ITSs. The DASH scheme adjusts the data rate of a call when it starts and finishes soft handoff. The performance of the DASH scheme is evaluated by analytical and simulation methods. Performances are evaluated with respect to the blocking probability, the handoff failure probability, and the carried traffic. Numerical results show that the proposed scheme can give relative good maintenance of calls and good throughput.

Ubiquitous Wireless Network will be the important infrastructure for ubiquitous information service in the future. Ubiquitous Wireless Network is objectively heterogeneous network, so vertical handoff is one of crucial topics. A vertical soft handoff scheme is proposed based on SIP using Wireless Access Gateway (RGW). RGW triggers and controls the handoff session to ensure same two-way delay of handoff and rate of zero-loss packet for real-time streaming media. Using M/M/1 queue model, delay of the scheme meets requirement of real-time streaming media.

Wireless networks are becoming a combination of more and more diverse and complicated networks. Handoff is a process to maintain data session continuity where mobile node changes from one base station coverage area to another base station area. Mobile maintains its existing connections via vertical handoff. In wireless environment single node mobility is known as host mobility and group of nodes moving together as single network is known as Network Mobility (NEMO). NEMO is extension of MIPv6, invented for reducing number of individual handoffs. To influence smooth mobility between these heterogeneous wireless access networks, expeditious and dependable vertical handoff (VHO) schemes are required. While taking VHO decision several parameters has to consider like received signal strength (RSS), addressable bandwidth, power intake, monetary cost, security, user predilection and etc. In this paper various handoff decision techniques based on different parameters for host mobility, and vertical handoff technique for Network mobility (NEMO) are discussed. Finally gave research issues and future research directions to NEMO.

To improve the local mobility performance of a wireless network, we present a new framework, namely Efficient Framework for Local Mobility (EFLoM). In EFLoM, we introduce three entities: Local Anchor Router (LAR), Wireless Access Gateway (WAG) and Mobile Node (MN). LAR is a router that is in charge of MN's IP mobility management. It keeps track of MN's movement, and delivers the MN's packets to its current location. AWAG is an access router that is responsible for managing the traffic flows within the same local mobility domain. In EFLoM, when Corresponding Node (CN) and MN connect to the same local mobility domain, packets are sent directly between CN and MN by WAG, without suffering sub-optimal routing problems. A MN is a mobile host which updates its data packets' header with its current location address before packets are sent out. To evaluate our new framework, we compare EFLoM with Hierarchical Mobile IPv6 Mobility Management (HMIPv6) [4] which is an existing protocol that has good performance for local mobility. Both analytical analysis and simulation result show that EFLoM can attain substantial improvements over HMIPv6 in terms of handover delay, end to end delay, traffic overhead, which therefore presents EFLoM as a new engineering alternative to existing MIPv6 based techniques.

This paper presents a new mobility protocol that supports multiple namespaces on IPv6 networks. Our proposed protocol framework allows a mobile node to specify a correspondent node by a name that is defined in any namespace as a node identifier. This technique removes certain restrictions on the space of node identifiers and allows mobile nodes to communicate with each other regardless of their location. Mobile nodes negotiate a pseudo node identifier which is unique between the two nodes, with a correspondent node that is identified by the name. We make this pseudo node identifier compatible with the IPv6 address format; we can thus use existing IPv6 applications with our proposed mobility framework. This framework is based on Location Independent Network Architecture (LINA), and provides mobility support in a simple fashion and with low protocol overhead. We also demonstrate how to provide anonymity to our mobility protocol by using a dynamic pseudo node identifier.

The Proxy Mobile IPv6 (PMIPv6) is a network localized mobility management protocol that is independent of global mobility management protocols. In a single mobility domain (LMD), the mobile node (MN) is not involved in any IP mobility-related signaling and uses only its PMIPv6 home address for all its communication. Subsequently, when the MN moves into another LMD, the MN must change its PMIPv6 home address. In such a circumstance, host-based mobility signaling is activated. Thus, the nature of the network-based mobility of the PMIPv6 cannot be retained. Additionally, if the MN does not support global mobility, it cannot maintain communication with its correspondent node (CN). In this paper, we propose a solution for global mobility support in PMIPv6 networks, called G-PMIPv6 that allows current communication sessions of a MN without mobility protocol stacks to be maintained, even when the MN moves into another LMD. Thus, G-PMIPv6 retains the advantages of the PMIPv6 for global mobility support. We then evaluate and compare network performance between our proposed solution and PMIPv6.

During interdomain handover, IPv6 node has to acquire new address at its new location. Once the L2 handover procedure is completed, mobile node (MN) starts its IPv6 configuration, using stateless (router advertisements) or stateful (DHCPv6 communication) mode. After the address is obtained, its uniqueness has to be verified, using Duplicate Address Detection (DAD) procedure. Depending on the interface type, this procedure may easily take more than 1000 ms. Assigned address can be used only after DAD procedure is complete, e.g. for informing corresponding nodes (CNs) about new MN location. DAD procedure introduces unwanted delays in handover and reconfiguration process. In the paper new mechanism that moves the burden of address uniqueness verification from mobile IPv6 nodes to static DHCPv6 servers is proposed. Proposed server-side DAD mechanism is presented, together with validation techniques used to verify its usefulness. The paper also proposes updated, recently introduced mechanism that enables IPv6 address acquisition and other configuration options in advance, before actual handover is performed. Mechanism itself and its verification techniques are discussed. Results of extensive simulation experiments performed in a mobile WiMAX network with IPv6 support, statistical analysis as well as areas of further study conclude this paper.

Mobile IP has seen slow deployment for two major reasons; the need for enhancing edge routers with Home Agent/Foreign Agent functionality and the fact that triangle routing in such systems is not efficient. Triangle Routing is defined as the route that must be taken through the Home Agent for any traffic sent by the Correspondent Node to the Mobile Node. This route is triangle in nature and longer than the normal path between the Corresponded Node and the Mobile Node. Many protocols and research efforts have been developed to solve this problem. Internet service Provider (ISP MBG) is one of the proposed techniques used for solving the triangle routing problem in conventional Mobile IPv4. This paper will provide a further study on the performance evaluation of Route Optimization in Mobile IPv4 based on ISP MBG scheme. The proposed technique has been implemented and tested on the Microsoft.net platform. Simulation results prove that the new framework has solved the Triangle Routing Problem in Mobile IP by providing a shorter route with a minimum transmission time for all the datagrams transferred between the Correspondent Nodes and the Mobile Nodes.

While the IETF standardization process of the Mobile IPv6 and Network Mobility (NEMO) protocols is almost complete, their large-scale deployment is not yet possible. With these technologies, in order to hide location changes of the mobile nodes from the rest of the Internet, a specific router called a home agent is used. However, this equipment generates resilience and performance issues such as protocol scalability and longer paths. In order to solve these problems, we describe and analyze a new concept called Home Agent Migration. The main feature of this solution is the distribution of home agents inside the current Internet topology to reduce distances to end-nodes. As is usually done for anycast routing, they advertise the same network prefix from different locations; moreover they also exchange information about their associations with mobile nodes. This produces a Global Mobile eXchange (GMX), an overlay network that efficiently handles data traffic from and to mobile nodes, and operates home agents as would an Internet eXchange Point (IXP). When a correspondent node needs to exchange packets with a mobile node, the data traffic will be intercepted by its closest GMX home agent and redirected to the home agent to which the mobile node is bound.

Though some studies involving general micro-mobility exist, micro-mobility research concerning a mobile node (MN) moving between Mobile Anchor Points (MAP) is lacking. In Hierarchical Mobile IPv6 (HMIPv6), a MN sends a binding update (BU) message to a MAP when the MN performs a handoff. This scheme reduces the handoffs and BUs performance costs. However, the total signaling cost of HMIPv6 rapidly increases with the number of corresponding nodes (CN) for a MN moving among MAPs. In this paper, we propose a scheme based on logical topology with autonomous configuration allowing a MN to move around between MAPs without performing a BU. We perform the performance evaluation for packet delivery and location update costs through a novel analytic approach. We show that the proposed scheme is approximately two times better than the existing one in terms of the total signaling costs through performance analysis. Furthermore, our scheme also reduces the location management cost effectively.

Code-division multiple-access (CDMA) cellular systems use soft handoff. Although the capacity of CDMA systems is interference-limited in nature, channel shortages may occur because soft handoff uses several channels simultaneously. To cope with this problem, we propose an improved handoff method that borrows channels from stationary calls participating in soft handoff and allocates the borrowed channels to handoff requests by moving calls when a channel shortage occurs. Borrowing from stationary calls is possible because these calls do not undergo fast-fading and do not require receiver diversity. The proposed method is designed to avoid increased interference resulting from channel borrowing. The proposed channel-burrowing handoff scheme is analyzed in a situation involving both moving and stationary calls. A comparison is made between the performances of the typical IS-95-based handoff scheme and the proposed scheme. Numerical results show that the proposed scheme is better than the IS-95 scheme in view of the handoff refused probability, the handoff queuing delay, and total interference.

Soft handoff techniques are generally used in the downlink of CDMA cellular systems. When there is traffic deviation, the communications quality differs between cells. Some methods of equalizing the quality, such as signal-to-interference ratio (SIR)-based power control methods and flexible cell control methods have been developed. The method described in this paper controls the transmission power ratio allocated to the mobile stations in a soft handoff region according to the traffic load. The SIR difference between cells can be reduced by controlling the power transmitted to the soft handoff mobile stations. We calculate an optimum power allocation ratio for minimizing the SIR difference for a given traffic deviation range and the downlink orthogonality factor.

Next generation wireless networks must be able to coordinate services between heterogeneous networks using a mobile terminal with multiple access interfaces. One of the challenges for continuous seamless mobility is vertical handoff which is the decision for a mobile node to switch for one network to another different type of networks. Moreover, how to select a desired target network is an important issue to balance against the network condition and user preferences. In this paper, the policies of multiple metrics to trigger a handoff while a mobile node is located in UMTS and WLAN/WiMAX are designed. The received signal strength (RSS) of neighbor networks predicted by the back propagation neural network is beneficial to perform handoff early. We propose a dwell time calculation depending to the user speed and moving pattern. If the RSS conditions are consistently true during dwell time, then unnecessary handoffs are avoidable. To select an optimal target network, policies in the merit function is presented. The weights of each handoff metric are dynamic to several networks. The results indicate that the proposed policy-enabled vertical handoff decision algorithm and network selection outperforms the other two approaches in reducing the number of vertical handoffs, Grade of Service (GoS) while increasing the average utilization per call of WLAN/WiMAX networks.